pinctrl: meson: Drop pinctrl_unregister for devm_ registered device

It's not necessary to unregister pin controller device registered
with devm_pinctrl_register() and using pinctrl_unregister() leads
to a double free.

This is detected by Coccinelle semantic patch.

Fixes: e649f7ec ("pinctrl: meson: Use devm_pinctrl_register() for pinctrl registration")
Signed-off-by: Wei Yongjun <weiyj.lk@gmail.com>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>